Wiring Line Voltage t-stat in alternative phase

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  #1  
Old 09-05-15, 10:08 AM
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Wiring Line Voltage t-stat in alternative phase

I am hooking up an electric 240 Volt heater with a line voltage t-stat. The heater is fan forced so the heater is working on 240 and the fan is 120.

Now I have it hooked up so the incoming is on L1/L2 and the outgoing to the heater is on T1/T2.

If I turn the temp up to 80, the fan and heater comes on. If I turn it down to 40, the heater goes off but the fan stays on.

How can I rewire this t-stat so that the fan also goes off when I drop it to 40??

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  #2  
Old 09-05-15, 10:40 AM
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You should be feeding the heater with at least three wires. Two hot legs for 240v and a neutral for the fan.

The fan would connect to the neutral and T1 OR T2.

Most electric heaters have a temperature sensor so that the fan only runs when the heating element is hot.
 
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Old 09-05-15, 11:13 AM
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The heater only has 2 wires
 
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Old 09-05-15, 11:50 AM
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If the heater only has two wires and they are 240v ..... how are you powering a 120v fan motor ?
Not connected to the ground wire......


Do you have a make and model or link to that heater ?



Just as a separate aside here....
With those thermostats... they have two sets of contacts L1/T1 and L2/T2. One set of contacts closes as soon as the thermostat is turned on. The other set of contacts opens and closes based on the temperature setting.
 
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Old 09-05-15, 01:14 PM
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"One set of contacts closes as soon as the thermostat is turned on"

What do you mean by this statement?

Isn't the stat always ON?
 
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Old 09-05-15, 01:21 PM
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You: The heater only has 2 wires
PJ: If the heater only has two wires and they are 240v ..... how are you powering a 120v fan motor ?
That answer is key to what you are doing.
 
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Old 09-05-15, 01:22 PM
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I guess what I'm trying to understand is what controls the other phase of the t-stat. One phase of the t-stat is controlled by the change in temperature.

What controls the other phase?? The instruction manual says breaks on positive off. But what is positive off??
 
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Old 09-05-15, 01:25 PM
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But:
If the heater only has two wires and they are 240v ..... how are you powering a 120v fan motor?
.
 
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Old 09-05-15, 01:44 PM
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But what is positive off??
When you turn the stat to OFF..... that is posutive off. Both legs are open.

It differs by thermostat but for example.....

You turn the thermostat from off to on. Even at the lowest temperature..... the L1/T1 connection is closed (shorted). When heat is called for..... the L2/T2 contact closes allowing 240v into the heater.
 
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Old 09-05-15, 04:48 PM
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With two wires coming out of the heater and an external wall thermostat it is impossible for the thermostat to shut off the heater without also shutting off its built in fan --- unless there is a defect in the heater where a live wire or part is touching the frame or other grounded part.

If the power cable from the panel goes first to the thermostat and a continuing cable goes from the thermostat to the heater, then a neutral, if needed, must be included in both of those cables, passing through the thermostat box (but not connected to the thermostat). A neutral may not be brought directly to the heater from elsewhere.
 
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Old 09-05-15, 06:04 PM
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I was wondering if there is a separate 120v feed for the fan. If so without a relay the thermostat if only 2-pole couldn't control the fan.

The bigger question is why would a 240v heater have a 120v fan? Sounds like a jerry-rigg not intended by the manufacturer.
 
  #12  
Old 09-05-15, 08:37 PM
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A 120/240 volt feed can power a 240 volt heater with built in 120 volt fan using a remote 2 pole line voltage thermostat. However the two poles might not switch on and off at precisely the same moment so it is possible for the fan to be running while the heat has shut off. (Not vice versa.)
 
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Old 09-05-15, 08:40 PM
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A 120/240 volt feed can power a 240 volt heater with built in 120 volt fan
Agreed but he has written there are only two wires.
 
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Old 09-06-15, 11:49 AM
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The OP has never said whether the thermostat is a 1 pole or 2 pole. I suspect he is using a 1 pole thermostat and using the ground wire as a neutral. His question is pretty simple, but the safety issue must be taken care of first before someone gets hurt!
 
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Old 09-06-15, 11:51 AM
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Now I have it hooked up so the incoming is on L1/L2 and the outgoing to the heater is on T1/T2.
The OP is using a two pole thermostat.
 
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